The present invention relates to the art of dental retraction cords, also referred to as gingival retraction cords.
Present practice in crown and bridge work technique makes use of cords such as the braided gingival retraction cord described in U.S. Pat. No. 4,321,038, issued Mar. 23, 1982 to Don D. Porteous. The cord or string, which is usually impregnated with a vaso-constrictor, is unwound from a spool or withdrawn from a container. The dental practitioner estimates the length required and snips the desired length from the spool. He then wraps the cord around the tooth and either ties a knot to hold the cord in position on the cervical portion of the tooth, or overlays several turns of the cord on the tooth to hold the cord in place.
The practitioner then tucks the cord between the tooth and the gum tissue, to retract the gum tissue to thus enable an accurate taking of an accurate impression of the tooth inclusive of its cervical portion. Some retraction cords are made of strands impregnated with vaso-constrictors such as Epinephrine, or aluminum potassium sulfate. To this end it is desirable to produce the retraction cords from materials which are liquid permeable to facilitate impregnation thereof with suitable medicaments. One of the most recent developments in the structure of a dental retraction cord is shown in the above U.S. Patent to Porteous. It includes, apart from the braided absorbent strands, one or more strands disposed at the core of the cord and being adapted to prevent the flattening of the cord when disposed in the gingival sulcus. The invention described in the above patent somewhat increases the convenience of application of the retraction cord. Yet, the cord is still relatively difficult to pack into the gingival sulcus due to its inherent pliability which is due to the need for selecting strands of absorbent material, usually cotton.